gnome-panel needs to be restarted. In a terminal window, type:
If your toolbar doesn't restart, type:
-ef | grep gnome-panel
In the second column, there is a number.
This is the process id (pid).
In the terminal...
This happens from time to time. Gnome has just lost your window
manager for some reason. (Check your quota) To fix it...
On the tool bar at the top of your window click...
In the box that opens up scroll down on the right to...